The invention relates to an apparatus on a combing machine for monitoring the noil percentage.
It is known to provide means for supplying and for combing out fibre material to be combed and means for forming at least one combed sliver, in which at least one arrangement is present for continuous automatic generation of a signal representing the noil percentage when the combing machine is running, the arrangement including at least one measuring device for the mass of supplied fibre material and at least one measuring device for the mass of combed fibre material and a calculating means for determining the noil percentage.
In the case of an apparatus according to WO 2005/001176 A, the noil percentage is determined indirectly, i.e. by measuring the quantity of fibre that runs into and out of a combing device. For that purpose, the combing device (combing head) is equipped with an arrangement device for determining the noil amount during operation, the arrangement comprising the following elements: for continuous determination of the incoming fibre amount (g/m), a thickness-measuring means and a sliver length-measuring means are associated with the intake rollers and delivery rollers respectively. The thickness-measuring means are displacement sensors, which measure the deflection of one roller of a pair of rollers and convert this deflection into electrical signals. A calibration in relation to the dependency of the amount of fibre (g/m) on the path deflection is effected. The sliver length-measuring means pick up the rotations of a roller and likewise generate electrical signals. In this apparatus the thickness of the incoming and outgoing fibre web is measured using feeler rollers. A drawback of this apparatus is the unsatisfactory measuring accuracy, since only the web thickness is measured and not the actual mass. Partial thick places in the webs falsify the measurement result. In addition, the web width is not constant, which is a prerequisite for a precise measurement. The calculated noil percentage for each of, for example, eight combing devices (combing heads), is output in the form of a table. The noil percentage (%) can also be represented in graph form over a period of time of, for example, 12 hours. Display of the noil percentages of the individual combing heads is effected in each case over relatively long periods of time. A correction of individual combs on the basis of the measurement results is possible only from time to time and only after the printouts or readouts, which reproduce a relatively long period of combing production, have been evaluated. There is no provision for a short-term fine adjustment. In practice, evaluations and, if applicable, adjustments, are regularly carried out by operational staff. It is also not possible to identify the reasons for undesirable variations from the readouts.